docs: def edit_distance_1(self, word):
          """ Compute all strings that are one edit away from `word` using only
              the letters in the corpus
  
              Args:
                  word (str): The word for which to calculate the edit distance
              Returns:
                  set: The set of strings that are edit distance one from the \
                  provided word """
          word = word.lower()
          if self._check_if_should_check(word) is False:
              return {word}
          letters = self._word_frequency.letters
          splits = [(word[:i], word[i:]) for i in range(len(word) + 1)]
          deletes = [L + R[1:] for L, R in splits if R]
          transposes = [L + R[1] + R[0] + R[2:] for L, R in splits if len(R) > 1]
          replaces = [L + c + R[1:] for L, R in splits if R for c in letters]
          inserts = [L + c + R for L, R in splits for c in letters]
          return set(deletes + transposes + replaces + inserts)